The correct answer is C) the ability to forbid people under 18 to marry without parental consent.
You forgot to include the question. You only attached the quote and the options, but no question at all.
So the question was: "Use the quote to determine the statement that describes a reserved power used by state governments."
So the correct answer is "the ability to forbid people under 18 to marry without parental consent."
Let's remember that reserved powers were not granted but also were not prohin¿bited by the United States Constitution. In the case of the United States, the best reference to these reserved powers can be found in the 10th Amendment to the United States Constitution. Here you can read that if the Constitution did not grant the Federal government a specific power, it is granted to the state governments.